drm/msm: Docs and misc cleanup

Fix a couple incorrect or misspelt comments, and add submitqueue doc
comment.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Acked-by: Christian König <christian.koenig@amd.com>
Link: https://lore.kernel.org/r/20210728010632.2633470-2-robdclark@gmail.com


Signed-off-by: Rob Clark <robdclark@chromium.org>